332 CLASS INSECTA. 



domen, which is, as it were, folded. The luminous matter 

 occupies the underpart of the two or three last rings of this 

 portion of the body, which are otherwise coloured, and usually 

 yellowish or whitish. The light which they spread is more 

 or less vivid, of a greenish white, or whitish, like that of the 

 different phosphori. It appears that these insects can vary 

 its action at will, which is observed, especially when they are 

 seized or held in the hand. They live a very long time in 

 vacuo, or in the different gases, except in nitrous acid, mu- 

 riatic and sulphureous gas, in which they die in a few minutes. 

 Their living in hydrogen gas renders it, at least sometimes, 

 detonating. Deprived by mutilation of this luminous part of 

 the body, they still continue to live, and the same part, thus 

 detached, preserves during some time its luminous property, 

 whether it be submitted to the action of the different gases, 

 or whether in vacuo, or in the free air. The phosphorescence 

 depends more on the degree of softness of the matter than on 

 the life of the insect. It may be reproduced by softening 

 this matter in water. In lukewarm water these insects shine 

 with vivacity, and are extinguished in cold water. It appears 

 that this fluid is the sole dissolving agent of the phosphoric 

 matter.* 



These insects are nocturnal. The males are often seen to 

 fly, like the Phalaenae, around lights, from which we may 

 conjecture that the phosphoric brilliancy emitted chiefly by 

 the females, is intended to attract individuals of the other 

 sex ; and if the larvae and nymphs of the species of our own 

 country be, as Degeer supposes, luminous, we should only 

 conclude from this, that the phosphoric substance is developed 

 from their very first age. It has been said that some males 



• Besides the experiments reported in the " Annales de Chimie," con- 

 sult the " Annales Generales des Sciences Physiques," by MM. Bory de 

 St. Vincent, Drapier, and Van Mens, t. VIII. p. 51, where the researches 

 of M. Grotthus on the phosphorescence of tlie Lampt/ris Italica are e;iven. 



